An intraluminal prosthesis is a medical device used in the treatment of diseased blood vessels. An intraluminal prosthesis is typically used to repair, replace, or otherwise correct a diseased or damaged blood vessel. An artery or vein may be diseased in a variety of different ways. The prosthesis may therefore be used to prevent or treat a wide variety of defects such as stenosis of the vessel, thrombosis, occlusion or an aneurysm.
One type of intraluminal prosthesis used in the repair of diseases in various body vessels is a stent. A stent is a generally longitudinal tubular device formed of biocompatible material which is useful to open and support various lumens in the body. For example, stents may be used in the vascular system, urogenital tract and bile duct, as well as in a variety of other applications in the body. Endovascular stents have become widely used for the treatment of stenosis, strictures and aneurysms in various blood vessels. These devices are implanted within the vessel to open and/or reinforce collapsing or partially occluded sections of the vessel.
Stents generally include an open flexible configuration. This configuration allows the stent to be inserted through curved vessels. Furthermore, this configuration allows the stent to be configured in a radially compressed state for intraluminal catheter implantation. Once properly positioned adjacent the damaged vessel, the stent is radially expanded so as to support and reinforce the vessel. Radial expansion of the stent may be accomplished by inflation of a balloon attached to the catheter or the stent may be of the self-expanding variety which will radially expand once deployed. Structures which have been used as intraluminal vascular grafts have included coiled stainless steel springs; helically wound coil springs manufactured from a heat-sensitive material; and expanding stainless steel stents formed of stainless steel wire in a zig-zag pattern. Examples of various stent configurations are shown in U.S. Pat. No. 4,503,569 to Dotter; U.S. Pat. No. 4,733,665 to Palmaz; U.S. Pat. No. 4,856,561 to Hillstead; U.S. Pat. No. 4,580,568 to Gianturco; U.S. Pat. No. 4,732,152 to Wallsten and U.S. Pat. No. 4,886,062 to Wiktor, all of whose contents are incorporated herein by reference.
A graft is another commonly known type of intraluminal prosthesis which is used to repair and replace various body vessels. A graft provides a lumen through which blood may flow. Moreover, a graft is often configured to have porosity to permit the ingrowth of cells for stabilization of an implanted graft while also being generally impermeable to blood to inhibit substantial leakage of blood therethrough. Grafts are typically tubular devices which may be formed of a variety of materials, including textile and non-textile materials.
A stent and a graft may be combined into a stent-graft endoprosthesis to combine the features thereof. The graft, however, in the stent-graft endoprosthesis should comply with the implantation requirements of the stent which often include collapsing the stent for placement at an implantation site and expansion of the stent for securement thereat. Grafts which cannot easily accommodate the longitudinal and/or radial dimensional changes from a unexpanded or collapsed state to an expanded stent often complicate the implantation of the stent-graft. For instance, some grafts are folded in the collapsed or unexpanded state and must be subsequently be unfolded to accommodate the expanded stent. The unfolding of the graft, however, often complicates the placement of the graft on the stent and the implantation of the stent-graft itself. Alternatively, noncontiguous grafts have been used with expandable stent-grafts. Upon expansion of the stent, however, portions of the noncontiguous graft often separate to accommodate the stent expansion. This separation leaves gaps in the graft structure thereby permitting the leakage of blood through these gaps.
Moreover, an intraluminal device, such as a stent, a graft or a stent-graft, may dilate over time after implantation within a bodily lumen. The dilation of the implanted intraluminal device is a radial enlargement of the device resulting from pulsating stresses or pressures present within the bodily lumen. The action of the pulsating stresses or pressures often fatigues the structure of the device resulting in radial expansion and possibly longitudinal foreshortening.
A variety of mechanical means have been used to attempt to limit device dilation. For example, U.S. Pat. No. 5,843,158 to Lenker et al. describes the use of generally inelastic frame rings circumferentially disposed along a radially contractible stent-graft. The frames are described as limiting the radial expansion. Such frames, however, must be integral to the stent and complicate the stent-graft geometry.
U.S. Pat. No. 5,843,158 to Lenker et al. further describes mechanical means for limiting radial expansion of a graft in a stent-graft. In one alternative, the stent graft includes an internal liner. The internal liner is described as an inelastic material and is folded within the stent graft. Upon radial expansion of stent-graft, the internal liner is described as further limiting the radial expansion of the stent-graft. Furthermore, a graft containing circumferential composite yarns is described as yet another alternative for limiting radial expansion. The composite yarns are described as having inexpansible yarns counter wound or braided over an elastic core yarn. The inexpansive yarns are described as limiting radial expansion of graft. These attempts to limit radial expansion of a stent-graft, however, result in complicated the stent-graft designs that have either additional liners or complex composite yarn designs.
Thus, there is a need for a graft that compliments the implantation of an expandable stent of a stent-graft endoprosthesis and limits dilation without the disadvantages of the prior art. In particular, there is need for a graft that is securably attached to the stent in both the expanded and unexpanded state which limits without complicating the mechanical dynamics of the stent or the graft.